Spatial division multiplexing optical mode converter

Abstract

Embodiments provide an optical device that includes a star coupler, a polarization bam splitter (PBS) and a polarization rotator. The star coupler includes a port at a first end face. The polarization beam splitter is optically coupled via a first side to the star coupler port, and is further optically coupled via a second side to a first port of an optical coupler. The polarization rotator is optically coupled between the polarization beam splitter and a second port of the optical coupler.

What is claimed is: 
     
       1. An optical device, comprising:
 a star coupler having a port at a first end face; 
 a polarization beam splitter optically coupled via a first side to said star coupler port, and optically coupled via a second side to a first port of an optical coupler; 
 a polarization rotator optically coupled between said polarization beam splitter and a second port of said optical coupler; and 
 a circular grating coupler having a plurality of radial ports coupled to said star coupler at a second end face. 
 
     
     
       2. The optical device of  claim 1  wherein the polarization beam splitter and polarization rotator are provided by a single component. 
     
     
       3. The optical device of  claim 1 , wherein said polarization beam splitter is optically coupled via said second side directly to said first port. 
     
     
       4. The optical device of  claim 1 , further comprising a laser coupled to said circular grating coupler via a tubular-core optical fiber. 
     
     
       5. The optical device of  claim 1 , wherein one or more of said star coupler, polarization beam splitter and polarization rotator are formed in a planar silicon layer over a silicon substrate. 
     
     
       6. The optical device of  claim 1 , wherein said polarization beam splitter is one of a first plurality of polarization beam splitters connected to said star coupler, said optical coupler is one of a plurality of optical couplers each being connected to a corresponding one of said polarization beam splitters of said first plurality, and further comprising a second plurality of polarization beam splitters connected to said star coupler, wherein a total number of said first and second pluralities of polarization beam splitters exceeds a number of said optical couplers. 
     
     
       7. An optical device, comprising:
 a circular grating coupler having a plurality of radial ports; 
 a star coupler connected to said radial ports via a first end face; and 
 a plurality of polarization beam splitters each being optically coupled via a first end to a second end face of said star coupler, each polarization beam splitter being optically coupled via a second end to one of a corresponding plurality of optical couplers. 
 
     
     
       8. The optical device of  claim 7 , further comprising a plurality of polarization rotators, each polarization rotator being coupled to a corresponding polarization beam splitter and a corresponding optical coupler. 
     
     
       9. The optical device of  claim 7  wherein the polarization beam splitter is configured to rotate the polarization of an optical signal propagating therethrough. 
     
     
       10. The optical device of  claim 7 , further comprising a tubular-core fiber optically coupled to said circular grating coupler. 
     
     
       11. The optical device of  claim 10 , further comprising a laser configured to couple an optical signal to said tubular-core fiber. 
     
     
       12. The optical device of  claim 11 , wherein said laser is further configured to provide light in an optical S, C or L band. 
     
     
       13. The optical device of  claim 7 , wherein said circular grating coupler, star couplers, and polarization beam splitters are formed from silicon. 
     
     
       14. The optical device of  claim 7 , further comprising ridge waveguides connecting said circular grating coupler to said star coupler. 
     
     
       15. The optical device of  claim 10 , wherein multiple propagation modes of said fiber are mapped to a single angular momentum mode of said circular grating coupler. 
     
     
       16. The optical device of  claim 7 , wherein said plurality of polarization beam splitters is a first plurality of polarization beam splitters, and further comprising a second plurality of polarization beam splitters connected to said second end face, wherein a total number of said first and second pluralities of polarization beam splitters exceeds a number of said optical couplers. 
     
     
       17. A method, comprising:
 forming a circular grating coupler having a plurality of radial ports; 
 forming a star coupler connected via a first end face to said radial ports; and 
 forming a plurality of polarization beam splitters such that each of said polarization beam splitters is coupled via a first end to a second end face of said star coupler, and each polarization beam splitter is optically coupled via a second end to an optical coupler. 
 
     
     
       18. The method of  claim 17 , further comprising connecting each of a plurality of polarization rotators between a corresponding one of said polarization beam splitters and a corresponding one of said optical couplers. 
     
     
       19. The method of  claim 17 , wherein ridge waveguides connect said circular grating coupler to said star coupler. 
     
     
       20. The method of  claim 17 , wherein:
 said plurality of polarization beam splitters is a first plurality of polarization beam splitters; 
 a second plurality of polarization beam splitters is connected to said second end face; and 
 a total number of said first and second pluralities of polarization beam splitters exceeds a number of said optical couplers. 
 
     
     
       21. An optical device, comprising:
 a star coupler having an end face; 
 a circular grating coupler having 2 n  input ports; and 
 a plurality of waveguides connecting said end face to said circular grating coupler, 
 wherein said waveguides are routed in groups having an integer multiple of two associated members, with the number of associated waveguides in each group sequentially decreasing from said end face to said circular grating coupler input ports.